This invention relates to a heated metal forming tool, and more particularly the invention relates to a heated metal forming tool for a hot blow forming, superplastic, or quick plastic forming operation.
Automobile body panels are typically made by forming low carbon steel or aluminum alloy sheet stock into desired panel shapes. Sheet panels may be made using conventional room temperature technologies such as stamping or sheet hydroforming. Sheet panels can also be made from elevated temperature forming technologies such as superplastic forming (SPF) processes and quick plastic forming (QPF) processes. The above-referenced high-temperature forming processes have the advantage of creating complex shaped parts from a single sheet of material. Such forming processes facilitate component consolidation, and allow an overall panel assembly to be manufactured with fewer panels and joints than would be possible if panels were formed with conventional stamping processes.
Superplastic forming processes generally utilize a metal alloy, for example, aluminum or titanium alloys that have high ductility when deformed under controlled conditions. Such metal alloys are capable of extensive deformation under relatively low shaping forces. Superplastic alloys are generally characterized by having tensile ductility in the range from 200 to 1,000 percent elongation. Generally, such a process involves heating an aluminum alloy sheet to a forming temperature in the range of from 400xc2x0 C. to 510xc2x0 C. and then stretch forming the sheet against a forming tool utilizing high-pressure gas.
Typical superplastic forming operations utilize low material deformation rates and consequently require slow press cycles such as 20 to 60 minutes to form shaped parts. However, high production requirements typically associated with automobile manufacturing would not allow for cycle times in the 20 to 60 minute range, as they would be economically unfeasible. Therefore, there is a need in the art for a metal forming process and associated tooling that can produce complex shaped parts with a lower cycle time.
There is disclosed a heated metal forming tool that includes an un-heated mounting plate attached to a press. There is also included a tool detail that is attached to the mounting plate. Insulation surrounds the tool detail to thermally isolate it from the mounting plate. The tool detail includes a plurality of heaters that are disposed in zones within the tool detail such that the temperature of various portions of the tool detail can be independently controlled.
The heated metal forming tool of the present invention has the advantage of providing a heated metal forming tool that is capable of maintaining a uniform temperature distribution, such that the cycle time of a forming process is decreased.
The heated metal forming tool of the present invention, has the further advantage of providing a tool including a plurality of heaters in zones such that the temperature of various portions of the tool can be independently controlled to maintain a uniform temperature gradient within the tool detail.
The heated metal forming tool of the present invention has the additional advantage of providing a tool that is thermally efficient, such that the energy needed to maintain the tool at the working temperature is lower than that used in heated-press systems.
The heated metal forming tool of the present invention has the additional advantage of providing a tool with a cool ( less than 130 F) exterior, such that other equipment may be placed in close proximity without being affected by high temperatures, and press operators can touch the tool exterior without injury.